i got a real sweet deal on some valves but there 2.02/1.60. i've heard i have to have the head reseated to fit them but im wondering if its gonna hurt performance goin that big?

 

hurt performance no. Thats the largest people go with i believe.
Killian suggested going with 2.00 in and 1.56 ex for a street car. You just have to be extra careful porting when your heads are set for vavles above 2.00 and 1.56

 

i've always run those valves in my older model smallblocks but never in an lt1. do you think its worth the extra money getting the heads done up to fit the larger valves?

 

Give Killian a call. 478 - 929 - 4252
i dont know if it costs more money or not.

 

what most people do is cut the heads as large as they can go and still have the 45 degree angle in the seat of the aluminum head. At tyhis point the seat of the head is pretty much the "right" size for a 2.00 and 1.57 I believe. By "right " size I mean to have the valve sealing at the edge of the valve. Alot of people use the 2.02/1.60 valves i these heads with no problem and with stock seats but there is a lil extra valve on each side of the seat thatthe air has to go around that would NOT be ther if ya use the "right" size valve (2.00/1.57). The 2.02/1.60'd do fit it there and do seal, but they are sealing more towards the back of the valve instead of the edge.
I would not change the seats to go with those valves, either run em with stock seats or get the 2.00/1.57 valves and do it that way. Changing seats would be the "right" way to put that valve in there but I doubt if the diff in cfm of a 2.00-2.02 or 1.57-1.60 valve is that much since the valve is getting closer to chamber walls and when ya figure in changing seats ya could have bought the other valves and saved $ or just used the 2.02/1.60's with stock seats and been very close. Some combinations may REQUIRE a larger valve but most people are looking for the best gain for the $ and for that reason changing seats just adds to the cost of stock heads and by the time ya buy valves, springs, retainers pay for porting, machining, etc, etc, ya could have bought some AFR's for that amount of $ and if the combo is really THAT serious that is what ya need anyway.

NightTrain66

 

ok nighttrain that explains it a little better. thanks for all the info. the only reason i was gonna run the 2.02 was because i was getting them brand new in the box for 75 bucks. but if i gotta spend another 200 getting them machined right then its not worth it. so now im off to buy springs thanks again guys

 

im putting 2.02 and 1.60 in mine becuase the guysaid he would cut new seats for the new vavles set up the springs and valves to the seat height i want for 50 bucks a head. so 100 bucks in all.thats machine work and all. so i figured why not.

 

If the $75 is for the 2.02 and 1.60's then the price seems good. If the price is $75 for intake and $75 for exhaust ($150 total) than ya could buy some new valves from alot of people for that price.

The 2.02/1.60 's is what alot of people run in these heads with no problems. If you have the heads off and your options are to run stock valves or these 2.02/1.60 's then i would go with the larger valves over the stock valves. You can get them to work with the stock seats and it would be better than stock for sure but if ya are buying new valves than ya should put a lil more $ with it and get the 2.00/1.57 to fit the seats correctly.

If the heads are off the car ya should do it but I would not pull the heads to do this. If ya are pulling em to port, and/or mill than do it....... but i would not pull the heads for this only. Also if ya change to larger valves make sure you or the machine shop blends the new valve jobs bottom cut to the portwork. If you are not able to get this done and the valve jobs bottom cut leaves a sharp ridge below the valve seat and/or if you use the larger valves with out unshrouding the valves then any flow gained by larger valves could probably be negated by these things. If ya are in doubt e-mail me or check with the machine shop and it may be better to go with stock diameter valves but a NICE valve job. I have seen very impressive #s with stock valves and minor bowl work that has been blended to a NICE valve job. If ya can not do the over size valves right than the sock valves and more $ valve job will probably give ya better results than the larger valves and "not so correct" valve job.

NightTrain66

 

depends on what power you plan on making. the vortec heads are basically the same as the lt1's and they have 1.94 and i think 1.50 and people are making 450 streetable hp with them so talk to your engine builder or better yet contact a company who deals in f-body's and see what they have to say about your setup.

 

the price on the valves is 75 for all of them. the heads arent off yet but i will be pulling the motor in the month or so.im going to have the heads port and polished andjust more or less thought the bigger valves would be better flow = better hp. i just know you can have to much flow and actually hurt hp. didnt want to make that mistake. i guess i just need to get a price on doin the heads with the 2.02's and without have to do the extra machine work. thanks again guys
Rob

 

depending on the size cam you can probably get away with a mild pocket port and a good blend job on the bowls. you will be surprised at how little you can do and get alot out of it.

 

Search for recent threads on valvesizes... theres quite a few.

May learn somethin, may save $.. may not :P

 

You may spend less on the valves but you better be paying more on headwork to make them work! It's not just about the seats but also the surrounding material in the combustion chambers. Those large valves in the small LT1 combustion chamber are going to have plenty of shrouding. Of course the effects ripple down to everything. It can certainly be made to work but to do it correctly I wouldn't use the mindset of simply "how do I get these to fit on the seats".

 

Throw a set of 2.02/1.6 in without deshrouding the combustion chamber and you'll hurt flow... whoda thunk it.
Always run the biggest valve you can run providing you can deshroud the combustion chambers enough to make an improvement. Guys have been saying this for years but the limiting factor is in how much deshrouding you can do.... if not enough, then you move the valves and go from there..... 2.08/1.6 anyone?

-Mindgame

 

I'm using 2.02in/1.60ex valves. I had the seats enlarged for the bigger valves. The heads are fully ported, and here's how they flowed on a SuperFlow 600 flowbench at 28in. Hg:

Intake:
.100" 65.8
.200" 130.1
.300" 183.9
.400" 227.2
.500" 248.2
.600" 244.6
.700" 244.0
.800" 242.8

Exhaust:
.100" 95.1
.200" 136.3
.300" 168.0
.400" 188.6
.500" 203.7
.600" 210.8
.700" 214.0
.800" 217.1

One thing to keep in mind is, the intake peak flow isn't incredible, but the low lift flow is pretty decent. I put a 30 degree back cut on the valves to improve low lift flow (both intake and exhaust). I got closer to 260cfm out of the intake with a 45 degree back cut on the valves, but decided to trade some of that for lower lift flow. Obviously other guys are getting more peak flow out of their heads, but at a sacrifice for less low lift flow. I'm by no means a professional head porter, but ported my heads myself (also another reason they aren't flowing 270cfm+).

I think the 1.60 exhaust valves really helped increase my exhaust flow. The 2.02 intake valve I'm not sure was worth a ton, but I don't think it hurt.

Just my 2 cents.